A TEST for Alzheimer鈥檚 disease that could reveal its early signs decades before there鈥檚 any real brain damage may be literally staring us in the eye.
People with Alzheimer鈥檚 seem to develop a rare form of cataract made up of the same beta-amyloid protein that forms the clumps or plaques in the brain that characterise the disease.
Patients won鈥檛 notice the cataract because it forms behind the iris, not the pupil, and doesn鈥檛 affect vision. But it can be seen and measured through a simple device called a slit lamp, which makes it easy to spot the disease early on and monitor its development.
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Using animal studies and tissue from post-mortems, Lee Goldstein of the Massachusetts General Hospital in Boston and his team found that levels of the rogue protein in the eye seem to relate to the severity of build-up in the brain, potentially telling you how advanced the disease is. The brain tries to clear out the abnormal aggregates, but the lens can scarcely do this at all. So it might be possible to pick up the signs of Alzheimer鈥檚 in our twenties or thirties, says Goldstein, before we can detect the protein in the blood or brain.
There is no cure or way to reverse the damage caused by Alzheimer鈥檚. But researchers are looking for ways to halt the disease, so any marker that tells you about it before there is any cognitive damage would be invaluable, says Goldstein. 鈥淣o one thinks that鈥檚 possible. But that鈥檚 what we hope lens aggregates will do.鈥� Goldstein and his team are now about to begin a clinical trial to investigate just how good a marker the eye protein will be.
Arun Raina, an Alzheimer鈥檚 researcher from Case Western Reserve University in Ohio, says a good test will be important for measuring the effectiveness of drugs. 鈥淎t the moment we rely on psychological testing,鈥� he says. 鈥淏ut that鈥檚 not always reliable.鈥�
The discovery may have unexpected benefits. Metal ions seem to encourage beta-amyloid build-up, an idea first suggested by Goldstein鈥檚 colleague Ashley Bush, (New Scientist, 26 August 2000, p 36). Goldstein has found that chelating agents, which mop up the ions, can slow down protein build-up in the eye. We might be able to treat all forms of cataracts with chelating agents instead of surgery, he suggests.
